Condition responsive device



Jan. 21, 1947. M. H. MAY 2,414,756

CONDITION RESPONSIVE DEVICE Filed May 7, 1943 3nventor Patented Jan. Zl,1947 STATES CONDITION RESPONSIV E DEVICE Merle H. May, Minneapolis,Minn, assignor to Minneapolis-Honeywell Regulator Company, Minneapolis,Minn., a corporation of Delaware Application May 7, 1943, Serial No.486,103

7 Claims. (Cl. 177-311) This invention relates to the field of measuringand control devices, and comprises means for responding to any conditioncapable of presenting as a parameter attenuation of a mechanical signal.The invention is particularly adapted for use as an ice indicator foraircraft, and will be principally described in this connection; but

'it may also be embodied in test instruments'for batteries, end pointsin certain cooking and evaporating processes and chemical reactions,etc. It is an object of my invention to provide a system responsive toany condition capable, of presenting as a parameter attenuation o amechanical signal.

It is a further object of my invention to provide a new and improvedcondition responsive means.

It is a, further object of my invention to provide a new and improvedice indicating system.

It is a further object of my invention to provide a condition responsivedevice including a vibratile element, means imparting energy of normalvibration thereto, and indicator means for responding to the vibrationof the element, wherein the element is exposed to a condition having anattenuating or other perceptible effect on the normal vibration of theelement.

It is a further object of my invention to provide a new and improvedsensing element for an ice indicator system. i

It -is a still further object of my invention to provide a sensingelement for an ice indicator system including a vibratile element, meansimparting energy of normal vibration thereto, and indicating means forresponding to the vibration of the element, wherein the element isexposed to accretion of ice having attenuating or other perceptibleeffect on the normal vibration of the element.

Other objects and advantages of my invention will become apparent upon astudy of the specificatlon and the subjoined claims, and of the drawingwhich is appended. hereto and which is to be considered a part hereof,the single figure of which shows in a. schematic and partly sec-' tlonalmanner the construction and arrangement of certain elements making up anembodiment of my invention.

In general terms, the figure shows an electromc oscillator unit Ielectrically associated with a driving element ll of a sensing device I2rigidly mounted in an airfoil I 3. Separated from members I 0 and H by asuitable electrostatic and electromagnetic shield I4 are a pick-upelement l5 and an amplifier IS. The functional relationship betweenthese various members will be presently set forth.

Oscillator l0 comprises: a vacuum tube having a filament 2|, a cathode22, a grid 23 and a plate 24; an oscillation transformer 25 includlB inga primary winding 26 and a secondary 21;

a condenser 30; a coupling transformer 3| including a primary winding 32and a secondary winding 33; a source of plate current 34 and a source offilament current 35. Condenser 30 is 20 connected in parallel with theprimary 26 of transformer 25 to form a parallel resonant circuit whichstabilizes the frequency of oscillation of the oscillator at anarbitrary value, as is well known in the art.

.25 The plate circuit of the oscillator may be traced as follows:Positive terminal of plate supply 34, conductor 36, terminal 31 of theresonant circuit-comprising primary 26, conductor 40, condenser 30 andconductor 4Ithe resonant circuit,

30 terminal 39 of the resonant circuit, conductor 42, primary 32 oftransformer 3|, conductor 43, plate 24 of tube 20, through the tube tocathode 22, conductors 48, 44 and 45 and back to the negative terminalof plate supply 34.

The grid circuit of the oscillator may be traced as follows: grid 23,conductor 46, secondary 21 of transformer 25, conductors 41 and 48,cathode 22 of tube 20, and back to grid 23. It will be seen that by theaction of oscillation transformer 25, a, signal varying with the platecurrent of tube 20 is impressed 0n grid 23, thereby causing oscillationof the tube circuit at a frequency determined by the electricalcharacteristics of elements 26 and 30. Secondary winding 33 oftransformer 3| impresses the output of the oscillator upon conductorsand'5l.

Sensing device l2 may conveniently comprise a, housing 60 open at itsend and secured in any convenient fashion in airfoil l3. Mounted at one50 end of the housing by means of a mounting ring I as at. 66 and 61 tothe centers of diaphragms 62 and 88, respectively. It will thus be seenthat member 88 is arranged for'vibration with diaphragm 82 and that thediaphragm 88 acts as an outboard bearing for member 88. Members 82, 83and 88 are thus arranged for unitary vibration with respect to housing88.

Mounted in any convenient fashion within housing 88 is driving elementII, which comprises a magnetic member 18 .and an electromagnetic member1|. It will be understood that member 18 can also be an electromagneticmember having its magnetic energy provided by a suitable windingenergized from a source of electricity, but for the sake of simplicity Ihave 2 shown it as comprising a permanent magnet. The member mayconveniently take the form of a cup having an internal flan e 12 as itsopen end and a centralpillar 13', the latter having an flange 12 ofmagnet member 18, being unitarily mounted on member 88 b means of a disk11,

which may be fastened to member 88 by any con venient means such as apin 18. Output conductors 88'and II of oscillator I3 are connected tothe ends of coil18.

Also mounted in any convenient'fashion within housing 88 is pick-upelement I8 which comprises a magnetic member 88 and an electromagneticmember 8I. It-will be understood that member 88 can also be anelectromagnetic member having its magnetic energy provided by a suitablewindin; energized froma source of electricity, if desired. I have shownthis member as a permanent magnet having the form of a cup with aninternal flange 82 and a central pillar 83, the latter having an axialbore 88 to provide free passage for member 88. Member 88 is magnetizedso that the flange 82 is of one polarity and the end of pillar 83 is ofthe opposite polarity: in

the figure I have shown them as being north and south poles,respectively.

Member 8I comprises a coil of wire 88 which may be form --retaining ormay be mounted on a form 88. Coil 88 is arranged coaxial with pillar 88and member 88 for free axial movement in the annular space betweenpillar 83 and flange 82 of magnet 88. being unitarily mounted on member88 by means of a disk 81 which may be fastened to member 88 by anyconvenient means such as a pin 88. a

along the axis'of member 85. It will also be understood b properlyselecting the reactances'oi' an indicating device comprising a directcurrent meter I I3; a sourceof plate current I I I, a source of filamentcurrent H8, and a source of biasing current II8 which is connectedacross the terminals of potentiometer I I8 as by conductors I25 and I8I.Primary I88 of transformer I88 is connected as by conductors H1 and H8to the ends of coil.

The plate circuit of the amplifier may be traced as follows: thepositive terminal of plate supply I, conductor 12!, indicator 8,conductor I22, plate I84 of tube I88, through the tube to cathode I82,conductors I23 and I24 and back to the negative terminal of plate supplyH8.

The grid circuit of the amplifier may be traced as follows: grid I83 oftube I88, conductor I21, secondary I81 oftransformer I88, conductor I28,movable contact II2 of potentiometer II8, a portion of thepotentiometer, conductor I38, con-- ductor I28 and back to cathode I82of tube I88.

It will be obvious that any alternating potential appearing onconductors I I I and H8 will be impressed by transformer I88 on the gridcircuit of tube I 88, modulating the plate current accordingly.

The various members comprising invention may be grounded as indicated atI32, I33, I38, I38, and I88, if desired.

Operation cording to well known electrical principles, when thisalternating electrical potential is applied to coil 18 located in thefield of magnetic element I8, continuous axial mechanical vibration ofthe assembly is produced, and since the oscillator is constructed to bein' a stable electrical condition,

energy is provided uniformly to coil 18 and uniform mechanical vibrationof the assembly takes place.

As is also well known, mechanical vibration of coil 88 cutting the fieldof magnet 88 causes an alternating electrical potential having the samefrequency as the frequency of the mechanical vibration to be impressedacross the primary I88 of transformer I85. As I have pointed out, thetransformer acts to modulate thedirect current flowing in the platecircuit at the same frequency. Potentiometer H8 is adjusted to such aposition that a grid bias of the desired magnitude is maintained on thegrid independent of any incoming signal. Itwill be seen that this biasmay be either positive or negative as may be desired. Under theconditions I have outlined above, potentiometer I I 8 is adjusted togive a grid bias which will permit the passing of suillcientpiatecurrent to produce a maximum reading on meter II3. Due to thedetector action of tube I88, under the influence of appropriate gridbias, the current passing through meter H3 is not an alternatingcurrent, but a pulsating direct current, and since the selectedfrequency has been chosen to be well above that to the separate pulsesof which the meter is capable of giving individual response, the metergives an indication which is influenced jointly by the normal platecurrent of the tube and by an effect proportional to the amplitude ofthe pulsating current. The latter is itself proportional to the attestsamplitude of the signal impressed upon -transformer me. It will thus beclear that durin normal operation of the instrument, a maximum signal isgiven by the indicator, and any failure oi the circuit will immediatelybe evident to the operator by an indication of zero on the meter. Nowlet it be assumed that ice or appreciable thickness is formed upon theairfoil surface and diaphragm 62. One sheet of this ice accretion willbe to damp the mechanical vibration of sens= ing element it, that is todecrease its amplitude. a portion 01 the energy of vibration which isunif for supplied by oscillator is being absorbed by the layer of ice.Then the amplitude of the signal being impressed upon primary ass oftransformer it will be reduced, and this reduced signal will betransmitted through the tube and appear as a small indication on meterH3. Additional accretion of ice on the diaphragm pro duces additionalreduction in signal amplitude and therefore in indication of the meter,until at somepoint the mechanical vibration of member db and itsassembly may be completely stopped. In this case, the meter indicatesits minimum reading which is the no-signal plate current of the tube asinfluenced by the setting of the potentiometer flit.

Since various changes and substitutions withthe bounds of my inventionwill become apparent to those skilled in the art, upon a study or thepresent specification, I do not wish to be limited by details ofstructure herein set forth for purposes of illustration, but only by thesubjoined claims.

I claim as my invention: 1. A sensing element for an ice indicatorcompris ng a first diaphragm adapted to be exposed to ice accretion, asecond diaphragm, a member joining said dlaphragms at points spaced fromtheir edges to form an assembly, first magnetic means carried in part bysaid member ior uniformly supplying energy of normal vibration to saidassembly, accretion of ice on said first diaphragm altering acharacteristic of said vibration, and second magnetic means carried inpart by said member and electrically responsive to said alteredvibration.

7 their edges to form an assembly, first magnetic means carried in partby said member by which said assembly is vibrated in a predeterminedmanner when cyclical electrical energy is applied thereto in the absenceof accretion of ice on said first diaphragm and in a. difierent mannerupon accretion of ice thereon, and second magnetic means carried in partby said member for generating electrical energy commensurate with thevibration of said first diaphragm.

3. In a device of the class described, a housing, a pair of diaphregmsmounted spacedly in said housing, one of suid diaphragms being adaptedto be exposed to ice accretion, a plurality oi homopolar mangets fixedin said housing with respect to said diaphragms, a. member traversingthe central poles of said magnets and rastened to said diaphragms forunitary movement therewith, a plurality of coils mounted on said memberfor unitary motion therewith, one of said coils being adapted forenergization from a source of alternating current, whereby to cooperatewithone of said magnets to effect vibration of said member and saiddiaphragm, accretion of ice on said diaphragm affecting a characteristicof said vibration, one or said coils cooperating with one of saidmagnets to comprise a device electrically responsive to change in saidcharacteristic of said vibration, and indicating meansconnected to saidresponsive device to indicate the magnitude of said change. I

4. A sensing unit for an ice indicator comprising, in combination, firstand second spaced diaphragms, meansponnecting said diaphragms forvibration as a unitary structure, means for mounting said structure toexpose only said first diaphragm to ice accretion, and magnetic meansfor supplying said structure with energy of vi= bration having apredetermined characteristic which is variably ailected by variableaccretion of ice on said first diaphragm, and whereby electricalresponse is given to said vibration in accordance with saidcharacteristic thereof.

5. A sensing unit for an ice indicator comprising first and secondspaced diaphragms,

. means connecting said diaphragms for vibration as a unitary structure,means for mounting said structure to expose only said first diaphragm toice accretion, and means whereby said structure is supplied with nergyof vibration having a predetermined characteristic which is variablyaffected by variable accretion of ice on said first diaphragm, andwhereby response is given to said vibration in accordance with saidcharacteristic thereof.

6. A sensing unit for an ice indicator comprising, in combination, firstand second spaced vibratile members having stationary portions andvibratiie portions, means for independently supporting the stationaryportions of said members to expose only said first member to iceaccretion. a connecting member supported by said vibratile members andconnecting the vibratile portions 0t said members for vibrationtherewith as a unitary structure, and magnetic means, carried in part bysaid connecting member and in part in said mounting means, iorsupplyingsaid structure with energy of vibration having a predeterminedcharacterlstic which is variably affected by variable accretion of iceon said first member, and for giving electrical response to saidvibration in accordance with said characteristic thereof.

7. A sensing unit for an ice indicator comprising, in combination, firstand second spaced vibratile members having stationary portions andvibratile portions, means for independently supporting the stationaryportions of said vibra: tile members to expose only said first member toice accretion, a connecting member supported by said vibratile membersand connecting the vibratile portions of said members for vibration.therewith as a unitary structure, and means carried at least in part bysaid connecting member whereby said structure is supplied with energy ofvibration having a predetermined character istic which is variablyafiected :by variable ac-= cretion of ice on said first member, andwhereby response is given to said vibration in accordance with saidcharacteristic thereof.

